This invention relates to diesel powered locomotives; and more particularly, to a system and a method controlling the supply of fuel to the locomotive's engine. The method utilizes speed and load information for the engine, and other engine operating information, to dynamically react to changes in engine load or other conditions which impact the engine's fuel requirements, predict fuel demand in response to these changes so to control engine speed, optimize the power output of the engine, prevent oversupply of fuel to the engine, and substantially reduce residual smoke and other regulated emissions the engine may produce. The system and method employ an adaptive capability by which, over time, coefficients utilized in producing the dynamic response are optimized for the particular engine and the environment in which the engine operates.
Adaptive control systems for controlling operation of a locomotive's diesel engine are currently available to supply fuel to the engine based upon sensed air pressure and the power output demanded from the engine. These systems take into account engine protection schemes (such as over speed protection) that prevent damage to the engine if it attempts to perform beyond its capabilities for a particular set of operating conditions. Two factors not taken into account by current control systems are: a) the time it actually takes to combust the fuel delivered to the engine; and, b) combustion chamber cooling effects which result from supplying too much fuel to the engine. Among other factors, the time it actually takes to combust fuel delivered to an engine is determined by:
i) the engine's operating temperature;
ii) pressure within the engine; and,
iii) the engine's operating speed (rpm).
If too much fuel is supplied to the engine for a given set of operating conditions, some of the fuel will not be combusted. This results in an excessive amount of smoke being produced by the engine. Excessive smoke will result in the locomotive's operation exceeding allowable emission standards.
As importantly, delivering too much fuel to the engine does nothing to increase to the amount of power (torque) produced by the engine. If the amount of fuel delivered to the engine continues to increase, the temperature in the engine's combustion chambers (cylinders) will fall. This results in a loss of power and reduces the engine's efficiency. There is also a substantial increase in the cost of operating the locomotive because of the fuel being wasted, especially since the engine obtains no benefit from the oversupply of fuel.
Current control systems are essentially reactive systems. That is, when a change occurs which results in the engine demanding more or less fuel so to produce more or less power, the systems utilize static look-up tables which provide a predetermined listing of sets of engine conditions and corresponding engine fuel demand and an engine fuel delivery schedule. To transverse from one set of operating conditions to another when a change occurs, these systems move in a step manner so that movement from the old operating point to the new one occurs incrementally. This is not to say that current systems do not respond adequately to sensed changes; but rather that the response could occur much more rapidly, and hence improve overall efficiency of engine operation while still not exceeding emission levels or otherwise detrimentally affecting engine operation.
By implementing an overall control methodology using an adaptive control scheme for an engine control unit (ECU), it is now possible to provide a dynamic look-up table functionality that “learns” from a particular engine's past performance so as to tailor the system's response for a particular engine's fuel demands based upon the particular range of operating conditions experienced by the engine. This results in an efficient, faster responsive, and more powerful control methodology than is currently available.